Network devices

Repeater, hub, bridge, switch, access point, router, modem and firewall: the layer where each one decides, what it reads and the domain it separates.

The outline, topic by topic

Each topic is weighted the way the exam weighs it.

Repeater: what is it?
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A layer-1 device that regenerates and retransmits the signal to extend a link's reach, without reading any address.
It does not understand frames: it cleans up the weakened signal and sends it on. Everything it connects stays a single collision domain.
Which of these devices reads no address, neither MAC nor IP?
- The hub
- The bridge between two segments
- The corridor switch
- The Wi-Fi access point
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The hub
A hub repeats the electrical signal out of all its ports. The bridge and the switch read the destination MAC address, and so does the access point, to know which wireless station to deliver to.
The repeater and hub work at layer …, the bridge and switch at layer …, the router at layer ….
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The repeater and hub work at layer 1, the bridge and switch at layer 2, the router at layer 3.
A device's layer is that of the highest information it reads: nothing for a repeater, the MAC address for a bridge, the IP address for a router.
Hub: what is it?
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A multiport repeater: whatever arrives on one port comes out of all the others, and all ports share the same bandwidth.
It has no memory of addresses, hence possible collisions between all hosts. Today the switch has replaced it nearly everywhere.